How to 'Ping' a filter



A particularly useful technique for creating percussive sounds similar to those achieved by an LPG, but with much more variety/flexibility is to 'ping' a resonant filter:


 * Turn up the resonance on a filter until it is at the point of self oscillating and then back off very slightly.
 * feed a trigger or short gate into the audio input.
 * the audio output should produce a percussive hit, very like a basic LPG pluck. the pitch of this hit will be dependent on the frequency of the filter cutoff (if cutoff is changed then the resonance may need adjusting to keep it on the cusp of self oscillating).
 * optionally, applying an envelope or other contoured cv to the cutoff input will shape the percussive sound to create a more complex sound - for example, an ADSR with a medium attack time and some decay/release will sound like a 'water drop' effect.

this technique is great for synthesisng your own drums - a pinged bandpass filter at low frequencies will give an 808 kick drum sound, low pass filters pinged at a mid-range frequency will give a sound similar to that of the 'buchla bongo' or tomtom drums.

cool tip: some filters self oscillate at a low enough frequency to produce an LFO rate cv signal - if pinged at this frequency the result is a lovely decaying cv 'wobble'!